Link the text content of two text objects
this a script that uses the scene update handler to synchronize two text object content :


select the two text objects only
copy and paste the script and click run
once you edit one of the text objects the other one will get updated accordingly 




import bpy

obj1 = bpy.context.selected_objects[0].name
obj2 = bpy.context.selected_objects[1].name

def link_text_objects(scene):
    obj = bpy.context.active_object
    if obj.type == 'FONT':
        if obj.name == obj1 : 
            scene.objects[obj2].data.body = obj.data.body

        else :
            scene.objects[obj1].data.body = obj.data.body

bpy.app.handlers.scene_update_pre.append(link_text_objects)